In general, motors are applied to washing machines, water pumps for vehicles, and the like, and provide power by their rotational motions. Typically, a washing machine receives power of a drive motor located on the bottom of a basket and rotates. The power of the drive motor is transferred to a rotating axis of a load, in which the output shaft of the drive motor is indirectly connected to the rotating axis through a belt, or the output shaft of the drive motor is directly connected to the rotating axis. In recent years, in order to reduce noise, breakdown, and energy waste, and to improve the overall strength of a rotor, and further to promote improvement of a washing function, motors employing a direct connecting mode of a double rotor structure have been in the spotlight.
FIG. 1 is a cross-sectional view of a conventional motor structure for a full-automatic washing machine. The conventional motor rotationally drives a basket and an inner tub of the full-automatic washing machine, and includes: a stator 10 having a large number of cores 11 wound with a coil 12; inner and outer rotors 20a and 20b that are interconnected by a rotor support 23 and that are rotated by a magnetic circuit that is formed when electric power is applied to the coil 12 of the stator 10, in which inner and outer permanent magnets 22a and 22b are mounted in inner and outer back yokes 21a and 21b; and a rotating axis that is combined at the central portion of a support frame 24 that is extended and formed on the inner circumference of the rotor support 23.
In addition, a holder 31 having connectors for connection to a control board (not shown), that is, a driver of the motor is provided at one side of the stator 10. Here, connectors for connection of the holder 31 include a power feeding connector for applying power to the stator 10, and a position signal transmitting connector that is connected to a Hall sensor substrate 33 provided with Hall sensors 34, thus transmitting position signals of the rotors 20a and 20b. The connectors for connection of the holder 31 are connected to the outside through lead wires 32.
Meanwhile, if the control board of the motor receives the position signals of the rotors 20a and 20b detected by the Hall sensors 34, the control board discriminates the rotational speeds of the rotors 20a and 20b, compares the rotational speeds of the rotors 20a and 20b with predetermined target speeds, and controls the rotors 20a and 20b to rotate at the target speeds with a three-phase (that is, U-phase, V-phase, and W-phase) timing signal, depending on the comparison results. Specifically, the control board of the motor transfers pulse waveform generated by combination of the Hall sensors 34 to a drive unit, and selectively switches a switching transistor corresponding to each phase, to thus control a power which is supplied to each phase coil of the stator 10 from a power supply to thereby make the motor driven. Here, the stator 10 is configured to have nine coils 12, in which three coils are assigned to each of the U-phase, V-phase, and W-phase and connected in series, to then make three-phase coils connected to have a Y-connection structure. In this case, when the position signals of the rotors 20a and 20b are sequentially detected by the three Hall sensors 34, the control board of the motor sequentially applies the power to the two-phase coils 12 among the three-phase coils 12 at a certain angle, to thus make the switching transistor driven. In other words, a three-phase motor has three-phase end points that are connected to each other, and repeats three processes of making the current flow in one direction, the current flow in the other direction, and then the current turned off, from the standpoint of one phase.
In particular, the Hall sensors 34 are composed of a lead type, respectively. These lead type Hall sensors 34 are connected on the Hall sensor substrate 33 in which one end of the long lead is inserted into the Hall sensor substrate 33 and then manually soldered. In this case, the Hall sensor substrate 33 on which the Hall sensors 34 are mounted requires peripheral components, such as resistors, capacitors, around integrated circuit (IC) chips that generate the position detection signals of the rotors 20a and 20b, and has essentially a need to perform a surface mount work. However, the conventional Hall sensor mounting structure requires that the Hall sensors 34 should be protruded in a direction perpendicular to the Hall sensor substrate 33 and arranged at the side surface of the inner rotor or outer rotor, in order to detect the rotational positions of the rotors 20a and 20b, since the Hall sensor substrate 33 is disposed in a horizontal direction at one side surface of the stator 10 along the circumferential direction of the motor. Therefore, according to the conventional art, long lead type Hall sensors 34 are mounted on the Hall sensor substrate 33, and one end of the long lead is manually soldered since it is not nearly possible to perform a surface mounting work. As a result, since the Hall sensors 34 may be seceded from the Hall sensor substrate 33 due to the bad soldering, and thus the poor contact may occur, there is a limit to have good reliability between the Hall sensors 34 and the Hall sensor substrate 33.
In addition, the Hall sensor substrate 33 is coupled at a state where the Hall sensors 34 have been inserted into Hall sensor insertion holes provided on the stator 10. The conventional Hall sensor mounting and assembling structures go through a manual insertion and assembly process of directly inserting Hall sensors on a Hall sensor substrate or requiring a separate soldering process. As a result, such a manual insertion and assembly process may cause a motor production cost to rise, and make mass production difficult. Thus, the Hall sensor substrate 33 needs to be made into a structure of being coupled to the stator 10 to facilitate mass production.
In addition, the holder 32 is manufactured into a structure of integrating power feeding connectors with position signal transmission connectors and thus when any one connector is out of order, all connectors need to be replaced to thereby cause unnecessary costs.
In addition, the conventional rotor has a structure that the back yokes 21a and 21b are inserted into the rotor support 23 that accommodates the stator and then the permanent magnets 22a and 22b are fixedly coupled on the back yokes 21a and 21b. In this case, the stator 10 always emits heat from the coils wound on the stator 10 when power is applied to the coils for rotation of the rotor, and accordingly a heat dissipation structure is required to ensure stability of a motor-driven environment. In particular, in the case of a double-rotor type motor, the inner rotor 20b and the outer rotor 20a are provided, to thus emit heat of hotter temperature than one rotor type motor when power is applied to the coils 12. As a result, needs on the heat dissipation structure in the double-rotor type motor are even greater than those of the mono-rotor type motor.
Conventionally, in order to implement such as a heat dissipation structure, height of the stacked stator core 11 is heightened, or capacities of the permanent magnets 22a and 22b in the rotor are enlarged, to thereby increase the torque of the motor, and to thus minimize the load of the stator coils 12 to suppress the amount of heat generated.
However, the conventional motor has no heat dissipation structure of dissipating heat generated from the stator coils, to thus degrade performance of the motor and shorten the life span of the motor.